Endogenous endothelin-1 limits exercise-induced vasodilation in hypertensive humans

Essential hypertension is a common disorder, associated with increased endothelin-l-mediated vasoconstrictor tone at rest. We hypothesized that increased vasoconstrictor activity of endothelin-1 might explain why the normal decrease in peripheral vascular resistance in response to exercise is attenuated in hypertensive patients. Therefore, we investigated the effect of endothelin A (ETA) receptor blockade on the vasodilator response to handgrip exercise. Forearm blood flow responses to handgrip exercise (15%, 30%, and 45% of maximum voluntary contraction) were assessed in hypertensive patients and matched normotensive subjects, before and after intra-arterial infusions of the ETA receptor antagonist BQ-123; a control dilator, hydralazine; and placebo (saline). Preinfusion (baseline) vasodilation in response to exercise was significantly attenuated at each workload in hypertensive patients compared with normotensive subjects. Intra-arterial infusions of hydralazine and saline did not increase the vasodilator response to exercise in either hypertensives or normotensives at any workload. The vasodilator response to exercise was markedly enhanced after BQ-123 at the 2 higher workloads in hypertensives (157 +/- 48%, P < 0.01; 203 &PLUSMN; 58%, P < 0.01) but not in normotensives. This suggests that the impaired vasodilator response to exercise in hypertensive patients is, at least in part, a functional limitation caused by endogenous ETA receptor-mediated vasoconstriction. Treatment with endothelin receptor antagonists may, therefore, increase exercise capacity in essential hypertension.

The Limits of Rational Choice: New Institutionalism in the Test Bed of Central Banking Politics in Australia

This paper tests the explanatory capacities of different versions of new institutionalism by examining the Australian case of a general transition in central banking practice and monetary politics: namely, the increased emphasis on low inflation and central bank independence. Standard versions of rational choice institutionalism largely dominate the literature on the politics of central banking, but this approach (here termed RC1) fails to account for Australian empirics. RC1 has a tendency to establish actor preferences exogenously to the analysis; actors' motives are also assumed a priori; actor's preferences are depicted in relatively static, ahistorical terms. And there is the tendency, even a methodological requirement, to assume relatively simple motives and preference sets among actors, in part because of the game theoretic nature of RC1 reasoning. It is possible to build a more accurate rational choice model by re-specifying and essentially updating the context, incentives and choice sets that have driven rational choice in this case. Enter RC2. However, this move subtly introduces methodological shifts and new theoretical challenges. By contrast, historical institutionalism uses an inductive methodology. Compared with deduction, it is arguably better able to deal with complexity and nuance. It also utilises a dynamic, historical approach, and specifies (dynamically) endogenous preference formation by interpretive actors. Historical institutionalism is also able to more easily incorporate a wider set of key explanatory variables and incorporate wider social aggregates. Hence, it is argued that historical institutionalism is the preferred explanatory theory and methodology in this case.

The Solomon Island: The limits of intervention

Binoy Kampmark Criticises the Basis of Australia's New Strategic Thinking for the Pacific Region

Transition to raloxifene with and without low-dose estrogen therapy in postmenopausal women: effects on serum lipids and fibrinogen - a pilot study

Objective To compare the effects of transferring from low-dose transdermal estrogen to raloxifene (RLX), with a phase of alternate-day RLX therapy with or without low-dose transdermal estrogen, on serum lipids and fibrinogen in postmenopausal women previously administered estrogen plus progestogen therapy. Methods Sixty postmenopausal women (mean age 55 years) were randomized to one of two treatment groups: RLX + low-dose transdermal estrogen (RLX + E) or RLX + placebo. The study consisted of four 8-week phases: phase I (all subjects low-dose transdermal estrogen 25 mug/day), phase II (double-blind RLX 60 mg every 2nd day in combination with either low-dose transdermal estrogen or placebo), phase III (all subjects RLX 60 mg every 2nd day + placebo) and phase IV (all subjects RLX 60 mg/day + placebo). Results No significant differences existed between groups for baseline measurements prior to phase I. In phase I, for all subjects combined, total cholesterol and low-density lipoprotem cholesterol both showed a significant increase (median increase of 0.2 mmol/l, p = 0.008 and 0.4 mmol/l, p < 0.001, respectively), while triglycerides decreased significantly (median decrease of 0.2 mmol/l, p < 0.001). For the primary analysis (phase II to phase IV), the mean change from baseline observations showed no significant differences between the therapy groups for serum lipids, fibrinogen, vital signs or weight. In the comparison phase (phase II), changes in serum lipids, fibrinogen, vital signs and weight were not significantly different between groups. Conclusion Gradual conversion to RLX from low-dose transdermal estrogen, with a phase of alternate-day RLX therapy with or without low-dose transdermal estrogen, does not have any effect on the serum lipid profile or fibrinogen level.